一、The function of crystal oscillator -- the basic concept of crystal oscillator
Crystal oscillator is a clock element commonly used in the circuit, its full name is called crystal oscillator, which is made of quartz crystal sheet with piezoelectric effect.Its purpose is to generate the original clock frequency, which is amplified or reduced by the frequency generator into the various bus frequencies in the computer.Quartz resonator has the advantages of small size, light weight, high reliability and high frequency stability, so it is used in household appliances and communication equipment.Quartz resonators have high frequency stability, so they are mainly used as resonant components in oscillation circuits that require very stable frequency.
二、The function of crystal oscillator -- the symbol representation of crystal oscillator
The crystal oscillator is structurally divided into two-legged crystal oscillator and three-legged crystal oscillator, and their representation in the circuit is shown in the following figure.
三、The role of crystal oscillators - what are they?
Crystals A crystal that converts electrical and mechanical energy into each other works in a resonant state to provide stable, precise single-frequency oscillation.Under normal operating conditions, the absolute accuracy of ordinary crystal frequency can reach 50%.Advanced accuracy is higher.Some crystal oscillators can also be adjusted by the applied voltage in a certain range of frequency, also known as the voltage controlled oscillator (VCO).
四、Four, the role of crystal oscillator is mainly divided into the following:
1. Provide the basic clock signal for the system.Usually a system shares a crystal oscillator to facilitate the synchronization of the various parts. Some communication systems use different crystal oscillators for the fundamental frequency and RF frequency, and keep synchronization by means of electronic frequency adjustment.
2. Crystal oscillator and PLL circuit are used together to provide the clock frequency required by the system.If different subsystems require different frequency clock signals, different phase-locked loops connected to the same crystal oscillator can be used to provide them.
Knowledge extension - the working principle of crystal oscillator
Crystal oscillator is short for crystal oscillator. It can be equivalent to a two-terminal network of a capacitor and a resistor in parallel and then a capacitor in series, as shown in the figure below.Electrotechnically, this network has two resonant points, divided by the higher frequency and the lower frequency, of which the lower frequency is series resonance and the higher frequency is parallel resonance.Due to the characteristics of the crystal itself, the distance between the two frequencies is quite close. Within this very narrow frequency range, the crystal oscillator is equivalent to an inductor. Therefore, as long as the two ends of the crystal oscillator are connected in parallel with appropriate capacitors, it will form a parallel resonant circuit.This parallel resonant circuit can be added to a negative feedback circuit to form a sinusoidal oscillator circuit, because the crystal oscillator equivalent to the inductor frequency range is very narrow, so even if the parameters of other components change greatly, the oscillator frequency will not change very much.
Extension of knowledge - classification of crystal oscillators
Crystal oscillator is also divided into two types: passive crystal oscillator and active crystal oscillator.Passive crystals require an oscillator in the DSP chip, and there is a recommended connection method on the capacitor.Passive crystals do not have the problem of voltage, the signal level is variable, that is, according to the starting circuit, the same crystal can be applied to a variety of voltages, can be used in a variety of different clock signal voltage requirements of the DSP, and the price is usually lower.
Active crystal oscillator does not need DSP internal oscillator, the signal quality is good, relatively stable, and the connection mode is relatively simple, do not need complex configuration circuit.
Seven, the role of crystal oscillator - crystal oscillator application
The application of crystal oscillator is very wide, crystal oscillator of the four application fields.
1. Mobile handheld devices: The most common mobile handheld devices are smart phones. In addition, typical mobile devices include iPad, handheld game consoles, handheld POS terminals, etc.
2. Consumer electronics: usually including laptops, cameras, video cameras, earphones, stereos, tablets, etc.
3, communication network: in the communication network is usually divided into wired communication and wireless communication.The technical fields of wired communication include optical transmission network, data processing, connection function, etc.The technical areas covered by wireless networks usually include baseband, connection interface, radio, etc.
4, medical electronics: common medical electronic equipment include: X-ray imaging, magnetic resonance imaging, ultrasonic system, endoscope, etc.